It is generally known that CFP skin shells can be reinforced with CFP stringers in order to withstand high loads in aircraft, with as little additional weight as possible. In this case, a distinction is essentially drawn between two types of stringers: T stringers and Ω stringers.
T stringers have a cross section composed of a base and a stem. The base forms the connection surface to the skin shell. The use of skin shells reinforced by T stringers is widespread in aircraft construction.
Ω stringers have an approximately top-hat-shaped profile, whose ends are connected to the skin shell. Ω stringers can either be adhesively bonded to the likewise cured shell when in the cured state themselves, or they can be cured at the same time as the shell using a wet-in-wet process. The latter is desirable because this is better from the process engineering point of view. However, supporting cores or moulding cores are required for wet-in-wet production of skin shells reinforced with Ω stringers, in order to fix and support the dimensionally unstable fibre semi-finished products in the desired Ω shape during the production process. Skin shells with Ω stringers have the advantage over T stringers that the infiltration capability during an infusion process for introduction of a matrix, for example of an epoxy resin, into the fibre semi-finished products is better. Infusion processes may be more cost-effective than other known methods for producing fibre composite components, such as the prepreg process, because this allows the use of lower-cost fibre semi-finished products.
However, one problem that arises in the production of Ω stringers is that the material used at present for the supporting core or moulding core is costly and can be removed only with difficulty after the formation of the Ω stringers, so that the material which remains in the stringers disadvantageously contributes to the total weight of the aircraft.